Stents are devices that are inserted into a vessel or passage to keep the lumen open and prevent closure due to a stricture, external compression, or internal obstruction. In particular, stents are commonly used to keep blood vessels open in the coronary arteries and they are frequently inserted into the ureters to maintain drainage from the kidneys, the bile duct for pancreatic cancer or cholangiocarcinoma or the esophagus for strictures or cancer. Nonvascular stenting involves a range of anatomical lumens and various therapeutic approaches, however, accuracy of installation is universally important.
In order to serve its desired function, the stent must be delivered precisely and oriented correctly. In order to facilitate the delivery of stents, medical device companies began to design deployment apparatuses that allow physicians to deploy stents more precisely. Unfortunately, guidance of the stent has substantially remained a function of physician skill resulting from substantial practice. This fact has become particularly evident with the advent of radially expanding stents. If after full deployment of the stent, the physician discovers the stent has been implanted incorrectly, there is no conventional way of correcting the error short of removing the stent. In particular, as a rule of thumb, once the exterior catheter, of conventional delivery devices, has been retracted beyond 60%, it generally cannot be realigned with respect to the stent. As a result, physicians must be sure of their stent placement prior to deploying the stent beyond the 60% point. We will refer to this 60% point throughout the application as the critical deployment point.
Conventional stent delivery devices, however, do not have any safety mechanism to prevent excessive deployment of a misaligned stent. In fact, conventional delivery devices require the physician to estimate extent of deployment, which results in either overly conservative or excessive deployment—both of which leads to stent misplacement.
An additional limitation of conventional stent delivery devices is the distal tip of conventional stent delivery devices are not adequately designed to (1) facilitate the clearance of obstructed lumen, or (2) facilitate the removal of the delivery device once the stent is radially expanded. In particular, most distal tips are not configured to comfortably guide the delivery device through a diseased or occluded lumen so that the stent can be delivered in the most beneficial location. Moreover, once the stent is radially expanded conventional designs rely exclusively on dimensional mismatching to ensure proper removal of the delivery device. In the event the stent does not adequately expand to preset dimensions, a conventional delivery device would be stuck in the patient until some invasive procedure is performed to remove it and the defective stent.
Therefore, there remains an existing need for a stent deployment apparatuses that has a safety mechanism to prevent excessive deployment of a misaligned stent. Preferably it would be desirable if the safety mechanism had a physical and/or audible indication means to inform the physician when she has reached maximum reversible deployment. As an additional safety feature, there is an existing need for a distal tip designed to allow for the removal of the deployment apparatus even if the stent does not radially expand to its preset expansion diameter. An existing need also exists for a stent deployment apparatus that has a distal tip adequately configured to navigate through diseased and/or occluded lumens so that the stent can be delivered to this target area.
There also remains an existing need for a stent deployment apparatus that increases physician control during stent deployment. Moreover, there exists a need for a stent deployment apparatus that allows for the insertion of an optical scope to facilitate stent delivery.